Scanning probe microscope and method for obtaining topographic image, surface potential image, and electrostatic capacitance distribution image

A scanning probe microscope comprising:

• a probe having a lever and a probe tip, the probe tip being disposable proximate a surface of a specimen;
• an oscillator for oscillating the probe at a resonant frequency .omega..sub.r of the probe;
• AC signal generating means for applying an AC voltage between the probe tip and the specimen to generate an alternating electrostatic force to oscillate the probe at a composite frequency having an amplitude component at a first frequency .omega. and an amplitude component at a second frequency 2.omega.;
• displacement detecting means for detecting an amplitude and a frequency of oscillation of the probe;
• displacement phase detecting means receptive of outputs from the displacement detecting means, the oscillator, and the AC signal generating means for detecting the respective amplitude components at frequencies .omega..sub.r, .omega. and 2.omega. of the probe oscillation and for determining a phase difference between the amplitude component at .omega..sub.r and an output signal of the oscillator;
• positioning means responsive to the phase difference for rapidly separating the probe and the sample when the probe tip comes in contact with the sample;
• such that a surface potential image of the specimen may be produced in accordance with the .omega. amplitude component of the probe oscillation, an electrostatic capacitance distribution image of the specimen may be produced in accordance with the 2.omega. component of the probe oscillation, and a topographical surface profile image of the specimen may be produced in accordance with the .omega..sub.r component of the probe oscillation.

A scanning probe microscope comprising:

• a probe having a probe tip attached to an electroconductive lever;
• oscillator means for oscillating the probe in close proximity to a specimen;
• displacement detecting means for detecting the probe oscillation and outputting a displacement signal in accordance with a change of a resonant amplitude of the probe and a phase of the probe oscillation around a resonance frequency of the lever;
• positioning means for relative positioning of the probe tip with respect to the specimen in X and Y directions and for controlling the distance between the probe tip and the specimen in a Z direction;
• means for applying an AC voltage between the probe and the specimen to generate an alternating electrostatic force to oscillate the probe at a first amplitude component having a first frequency .omega. and a second amplitude component having a second frequency 2.omega.;
• means for applying a DC voltage between the probe and the specimen so as to maintain the average value of an .omega. amplitude component of the probe oscillation at zero to enable the calculation of a surface potential of the specimen in accordance with the DC voltage and to enable the calculation of an electrostatic capacitance of;
• wherein the positioning means is responsive to a phase difference between an output of the oscillator means and the displacement signal for rapidly separating the probe and the specimen due to a large phase delay when the probe collides with a surface of the specimen to thereby enable detection that a measured value at that point is inaccurate and to enable the setting of a correct control parameter to control the distance between the probe and the sample in the Z direction in order to avoid a variation in the measured surface potential of the specimen due to the collision.

A method for obtaining a surface topographical profile, a surface potential distribution and an electrostatic capacitance distribution of a specimen using a scanning probe microscope having a probe comprising an electroconductive lever and a probe tip, the probe tip being disposable proximate a surface of the specimen, the method comprising the steps of:

• applying a resonance signal having a frequency .omega..sub.r to oscillate the probe at a resonance frequency thereof in close proximity to a surface of a specimen;
• applying an AC voltage between the probe and the specimen to generate an alternating electrostatic force to oscillate the probe at a composite frequency having an amplitude component at a first frequency .omega. and an amplitude component at a second frequency 2.omega.;
• detecting the respective amplitude components at frequencies .omega..sub.r, .omega. and 2.omega. of the probe oscillation;
• determining a phase difference between the frequency component at .omega..sub.r and the resonance signal;
• detecting inaccurate data when the probe comes into contact with the specimen in accordance with the phase difference between the amplitude component at .omega..sub.r and the resonance signal;
• producing a surface potential distribution of the specimen in accordance with the .omega. component of the probe oscillation by scanning the probe with respect to the .specimen while measuring the surface potential of the specimen;
• producing an electrostatic capacitance distribution of the specimen in accordance with the 2.omega. component of the probe oscillation by scanning the probe with respect to the specimen while measuring the electrostatic capacitance of the specimen;
• and producing a topographical surface profile of the specimen in accordance with the .omega..sub.r component of the probe oscillation by scanning the probe with respect to the specimen.